Yes, running low on fuel can get you in trouble. Never run a bus below 1/4 tank, since the tank is mounted lengthwise and the slope of the road makes a big difference. I'm ashamed to confess, last November I ran Millicent out of fuel while climbing a long 8 % grade. I don't know why the factory does not put the pick-up-tube in the rear of the tank. Just consider the 1/4 mark to be the empty mark, and you are safe.
I have not heard of an Alison stick shift. Allison makes automatic transmissions. Your stick shift probably has an other name hidden somewhere. Regardless, you are in luck to have the stick shift, because a gasoline engine with an Allison generally gets something like half the fuel milage you report.
Starters are the same basic design on gasoline engines and diesel engines, and they do wear out. Sometimes the starter motor itself goes first, and sometimes the solenoid (which is attached to the starter and considered a part of it). Again, I've been there! Had to go to Reno and buy a new starter to get Millicent fired up after the 2007 burn. And I even suspected -- from the sound of it -- that the old starter was on its last legs! But I hadn't gotten around to dealing with it. Bad.
Carry a spare starter or, better yet, put it in now and be done with it.
Same with the alternator. And belts and hoses.
Noise, heat and fumes can be a nuisance with the engine in the front --both "all the way out front" and inside the bus.
With the engine all-the-way-out-front you can add insulation on the firewall. There is insulation specially intended for this purpose, and I would not fool around with anything else. One brand that comes to mind is DynaMat, but there are others just as good.
With the engine inside the bus, next to the driver, you can buy or fabricate a "slip cover". The old WanderLodge motor homes, which were based on the Blue Bird school buses, had this from the factory.
Post-Playa, I clean the interior with a combination of compressed air (and goggles), vacuum cleaner, and soap-n-water & brushes-&-rags. I pay no attention to the exterior or underside. Everything under a bus is a lot more resistant to Playa-Dust Corrosion than a bicycle chain is.